Model submarine enthusiasts have long sought a model submarine which can accurately simulate the maneuverability and characteristics of their real life counterparts. Perhaps the most difficult characteristics to simulate are those involving diving and maintaining a level run at a given depth. In order to achieve these characteristics, two design philosophies have been utilized in model submarine technology. These philosophies are known as the positive buoyancy system (or PBS) and the negative buoyancy system (or NBS). Unfortunately, there are serious disadvantages inherent to both philosophies.
In the PBS system, the model submarine is "trimmed" to be slightly positively buoyant when the ballast tank(s) is/are fully flooded. In this respect, the model submarine employing a positive buoyancy system is failsafe inasmuch as the boat cannot sink to the bottom in the event of a power failure. However, when submerged, model submarines employing PBS have great difficulty with simulating the maneuverability of its full size counterpart. This is due, at least in part, the the dynamic forces acting on the diving planes which are used to force the boat under the surface of the water. These forces make control of the angle of attack of these planes (which also maintains a level run at a given depth) most difficult to achieve, especially since the boat cannot be seen by the operator.
In the NBS system, the model submarine is "trimmed" to be slightly negatively buoyant when the ballast tank(s) is/are fully flooded. While enabling the model submarine to more closely maneuver like its full size counterpart (especially at periscope depth level), these systems are extremely disadvantageous in that should the model submarine's propulsion system fail, the boat will sink necessitating its manual retrieval.
In model submarines of all types, various complicated techniques have been employed to satisfactorily attempt to fill and purge the ballast during diving operations. Many models employ a reversible pump which will pump water into or out of one or more ballast tanks. Other models use free flooding of the tank(s), by opening a vent valve which communicates with the top of the tank, in order to take on a sufficient quantity of water to submerge. In order to surface, these models close the vent valve and then purge the water out of the bottom of the tank using compressed air, freon, or the like. To aid in "trimming", these models are more often than not provided with at least two ballast tanks, one fore and one aft, each ballast tank being provided with its own, separate, flooding and purging means. Alternatively, to aid in "trimming" some models utilize a weight carried by a servo-controlled travelling lead screw which shifts, thereby altering the model's center of gravity. In such methods, the weight is usually positioned in a ballast tank.
Most of the submarine kits presently on the market also require for each model to have various separate watertight compartments in order to house electric motors and electronics, servo-motors, and often the batteries. Watertight shaft seals are therefore required as bulkhead penetrations for propeller shafts, servo-actuator linkages and controls, wire penetrators and the like. These penetrations are all potential leakage sites which could lead to short circuiting, flooding, and power loss resulting in the loss of a submarine. As such, these seals and penetrations require precise and often costly sealing means to effect leak-tight integrity.
Thus, it can be seen that there remains a need to provide a model submarine having an improved design wherein it can maneuver more closely to its full size counterpart and still employ a positive buoyancy system for failsafe operation.